About historic bridges
What makes a bridge historic?
Bridges can be historic for several reasons, including significant engineering accomplishments, aesthetic details or association with important transportation projects. Historians use historic contexts to determine which bridges pose historic value. The National Park Service defines historic context as:
“…information about historic trends and properties grouped by an important theme in the prehistory or history of a community, State, or the nation during a particular period of time. Because historic contexts are organized by theme, place, and time, they link historic properties to important historic trends. In this way they provide a framework for determining the significance of a property and its eligibility for National Register listing. A knowledge of historic contexts allows applicants to understand a historic property as a product of its time and as an illustration of aspects of heritage that may be unique, representative, or pivotal.”
For bridges built before 1956, MnDOT developed historic contexts based on material type – metal, concrete, and masonry. MnDOT is currently working on the development of a context for bridges built from 1956 to 1970.
- Historic bridge list (PDF)
- Masonary-arch highway bridges (PDF)
- Reinforced concrete highway bridges (PDF)
- Historic iron and steel bridges (PDF)
How does MnDOT preserve historic bridges?
MnDOT has committed to preserving select bridges owned by the state. In addition to federal and state preservation laws that require full consideration of preservation, MnDOT has gone beyond these laws to commit to the public that these iconic structures will receive a higher level of maintenance and more rehabilitation work to ensure they remain in use and continue to serve the public for as long as possible.
Approximately 85 percent of the historic bridges in the state are under the control of local agencies. MnDOT provides guidance to local agencies on best practices for maintaining and preserving their historic bridge. The Management Plan for Historic Bridges in Minnesota (PDF) provides information on applicable laws, funding options, rehabilitation alternatives, and Minnesota’s innovative collaborative approach, where engineers and historians collaborate to find solutions to rehabilitating bridges.
What is the historic bridge programmatic agreement?
In 2008, the FHWA, the State Historic Preservation Office, the Corps of Engineers and MnDOT signed a historic bridge Programmatic Agreement (PDF) to streamline the federal historic review of both MnDOT and local bridge projects when federal funds were involved. Eliminating the need to evaluate every bridge over 50 years old before projects can begin has significantly reduced costs and project delays, saving Minnesota taxpayers millions of dollars every year. Now when a bridge project comes in for review, if the bridge is not historic, the project can be cleared without any additional studies or delays. Any proposed work on the historic bridge is reviewed to see if it can be done in a way to maintain the bridge’s historic integrity, while still meeting modern needs.
What are some quick facts about historic bridges in Minnesota?
- How old does a bridge need to be to be historic? 50 years old.
- Are all bridges more than 50 years old historic? No - there are about 200 historic bridges in Minnesota.
- How many bridges total are there in Minnesota? There are 19,000 bridges in our state (spans of 10 feet or greater).
How does MnDOT comply with accessibility standards?
MnDOT has worked closely with the ADA Access Board, local citizen groups, and others to find solutions to make historic bridges ADA-compliant. The work is sometimes complicated by limitations in the existing structure (such as narrow sidewalks), but on all of the 2010 and 2011 projects we were able to be ADA-compliant. Read more about accessibility and MnDOT.
Example - Shakopee Pedestrian Bridge:
The previously existing conditions on the Shakopee Pedestrian Bridge
consisted of barricaded sidewalks (due to the deterioration of the railing) and
no pavement markings on the road deck.
After rehabilitation, the bridge will provide accessible sidewalks for a
viewing area, and delineated bicycle and pedestrian lanes.